MONITORING ELECTRON-TRANSFER BY PHOTOACOUSTIC-SPECTROSCOPY IN NATIVE AND IMMOBILIZED THYLAKOID MEMBRANES

Photoacoustic spectroscopy was used to monitor photosynthetic electron transfer in native and immobilized thylakoid membranes. The photoacoustic parameter PHI prime //r (the percentage of absorbed energy that is stored in photochemical intermediates) and i//5//0 (the half-saturation modulated light intensity) were directly correlated to electron transfer rates. As previously shown, thylakoids immobilized in an albumin-glutaraldehyde matrix were more resistant to aging. The inhibitory effects of the immobilization procedure and of aging at 4 degree C were detected as a decrease in i//5//0 values. In analogy with enzyme kinetic analysis, the effect could be characterized as a competitive type of inhibition. Photoacoustic measurements are performed in conditions similar to a working bioreactor cell with regard to the sample preparation.